Kaolinite induced control of particulate lead and cadmium emissions during fluidized bed waste incineration

Abstract

Kaolinite was utilized as in-furnace sorbent to control submicron lead (Pb) and cadmium (Cd) emissions during waste incineration in a fluidized bed furnace. The secondary combustion chamber temperature ranged from 850 to 1000°C. The metal capture was investigated for aspects of chemical reaction, physical conglutination and control performance of submicron metal emission. Pb reacted with kaolinite and caused conglutination of nanoscale metal particles at a lower temperature than Cd. Emission control of submicron Pb was far more effective than that of submicron Cd, particularly below 950°C. For both Pb and Cd, there was capture limitation and an increase of kaolinite fraction above 3% could not further reduce the submicron metal emission. According to toxicity factors (5 Pb = 1 Cd) and the leaching fraction of submicron particles, the comprehensive performance of kaolinite was evaluated and numerous contradictory results were obtained.

Dehydroxylation and Structural Distortion of Kaolinite as a High-Temperature Sorbent in the Furnace

“…The temperature of municipal solid waste (MSW) incineration is usually 800-1200 • C, at which, semi-volatile heavy metals and alkali metals exist mainly in the form of chloride vapor, such as PbCl 2 , PbCl, CdCl 2 , CdCl, NaCl and KCl [40][41][42][43]. In the condition of in-furnace injection, the residence time of kaolinite in the furnace is usually less than 2 s, so 15-55% of hydroxyl groups or more would remain in kaolinite.…”

Study on Capture Performance on PbCl2 and CdCl2 using Kaolin Modified by Sodium Ions

“…Besides, many other factors in the actual waste incineration also had a significant influence the heavy metal capture performance, the impact extents and influence mechanism of these factors were different. Using PbCl 2 and CdCl 2 as source of heavy metals, capture efficiency of Pb by kaolin in the thermogravimetric reactor was above 80 %, [4] while that of Cd was only about 10 %. [5] While Yao et al used the similar thermogravimetric reactor to obtain the capture efficiencies of PbCl 2 and CdCl 2 by raw kaolin both about 40 %-50 % at 800 °C.…”

Mechanistic investigation of the influence of defects on armchair unburned carbon for PbCl2 adsorption

“…Pb mainly exists in coal, municipal solid waste, industrial solid waste and other solid wastes or fuels. 1 , 2 During the heat treatment or combustion of these solid substances or fuels, a large amount of lead evaporates and is discharged into the atmosphere together with high-temperature flue gas. 3 , 4 When the smoke cools to a certain point, the lead vapor condenses and partially forms PM1 (lung-accessible particulate matter) and even smaller PM0.1.…”